In some wireless communication systems, it may be useful to determine positions of wireless communication devices. Some techniques for determining positions of wireless communication devices involve determining distances between communication devices, and using distance measurements to calculate positions of the devices. A distance between two devices can be determined by transmitting a signal from one device to another, determining the time it took for the signal to travel between the two devices (time of flight), and then calculating the distance between the two devices based on the time of flight.
In some wireless communication systems, communications are scheduled using timing information, such as TSF (time synchronization function) time or a time of day. For example, in many communication systems, communication devices maintain respective local clocks, and each communication device uses its local clock for purposes of determining when the communication device should transmit, when to expect another communication device to transmit, etc.
In some wireless communication systems, each communication device uses its local clock for purposes of determining times of flight. For example, a first communication device may use its local clock for recording when the first communication device transmitted a first packet to a second communication device, when the first communication device received a second packet transmitted by the second communication device, etc., and then may use the recorded times to estimate a time of flight between the first communication device and the second communication device.
In some wireless communication systems, communication devices may negotiate a time period for performing distance measurements. During the negotiated time period, the communication devices should be prepared to transmit or receive signals for distance measurement, e.g., be tuned to a same channel during the negotiated time period. However, over time, local clocks of different communication devices will drift with respect to each other, which may cause degradation in performance and, in some situations, result in the communication devices missing distance measurement transmissions because of different determinations of when the negotiated time period begins and ends.